Solid state control circuit for use in vending machines

ABSTRACT

A solid state control circuit for a vending machine which is effective to apply an operating potential to a plurality of commodity selection switches upon an appropriate coin deposit in the coin mechanism. The operation of one of the commodity selection switches causes a product to be dispensed and at the same time causes elements of the control circuit to prevent the further dispensing of any additional products. After a product has been dispensed, an internal timing mechanism within the control circuit places it again in a condition to receive a coin deposit.

United States Patent Bockholt Sept. 4, 1973 [54] SOLID STATE CONTROL CIRCUIT FOR USE 3,428,157 2/1969 Patterson 194/2 IN VENDING MACHINES Primary ExaminerRobert B. Reeves [75] Inventor" a a ggg tgg m Assistant ExaminerThomas E. Kocovsky Att0rneyI-loward T. Markey et a]. [73] Assignee: Oak Electro/netics Corp., Crystal Lake, Ill. [57] ABSTRACT [22] Filed: Feb. 23, 1972 A solid state control circuit for a vending machine 1 pp No: 228,633 which IS effective to apply an operating potential to a References Cited UNITED STATES PATENTS 3/1966 Gerhart 194/10 plurality of commodity selection switches upon an appropriate coin deposit in the coin mechanism. The operation of one of the commodity selection switches causes a product to be dispensed and at the same time causes elements of the control circuit to prevent the further dispensing of any additional products. After a product has been dispensed, an internal timing mechanism within the control circuit places it again in a condition to receive a coin deposit.

19 Claims, 6 Drawing Figures 1 SOLID STATE CONTROL CIRCUIT FOR USE IN VENDING MACHINES SUMMARY OF THE INVENTION The present invention relates to a solid state control circuit for use in a vending machine or the like and has particular application to a reliably-operable simply constructed circuit of the type described.

Another purpose of the invention is a control circuit of the type described which permits a predetermined interval for dispensing the product selected and automatically returns the machine to a condition to receive a coin deposit after a product has been dispensed.

Another purpose is a vending machine control circuit of the type described which will automatically return the machine to a condition to accept coins if no vending operation takes place during a predetermined interval in which the machine was in a ready-to-vent condition.

Another purpose is a control circuit of the type described which will prevent operation of the dispensing mechanism more than once for each coin deposit.

Another purpose is a vending machine control circuit which eliminates all moving parts, thus preventing problems normally encountered, such as wear, foreign particles, misadjustments, contaminants, shock, and vibration and the like.

Another purpose is a control circuit of the type described which can function in a variety of different vending machines.

Another purpose is a vending machine control circuit of the type described which prevents dispensing of more than one product for each correct coin deposit.

Another purpose is a solid state vending machine control circuit arranged to be automatically reset to a condition to accept coins, a predetermined interval after the deposit of coins, even if a vending operation has not been completed, in order to prevent the burnout of components which are normally rated'for intermittent use. 7 I

Another purpose is a control circuit of the type de-- scribed which will not accept coins into the vending machine unless the applied power is sufficient to cause operation of the machine to dispenses product.

Another purpose is a solid state control circuit for use in a vending machine or the like which can interface with all presently-used coin mechanisms and electrical dispensing means. 7

Other purposes will appear in the ensuing specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 6 is an electrical schematic illustrating details of I the circuit of FIG. 5.

THE PRIOR ART product. The credit signal is stored in an electrome chanical relay. While storing the credit signal, this relay may close the circuit which provides power to a number of selector switches which can then in turn be oper-' ated to cause other relays to energize the mechanisms dispensing the product. Provisions are made in the circuitry so that only one selection can be made by the user for every credit signal supplied by the coin mechanism and every selection made cancels the stored credit signal.

The electromechanical devices which provide the necessary logic for the operation of a vending machine are subject to many shortcomings. The mechanical parts are subject to wear, requiring frequent adjustment. The correct operation of the system depends upon all parts functioning in a close time relationship.

. The relatively slow moving mechanical parts frequently will not stay in'the correct time relationship and may lose the established credit, resulting in the loss of money to the customer. A loss of the timing function may fail to cancel credit after a selection has been made, resulting in a substantial loss of revenue to the merchant.

Another problem arising from the slowness of the mechanical parts is that in some instances it is possible to trap the credit signal and effect the release of merchandise in excess of the amount equal to the establish credit by manipulation of the electrical power applied to the machine or by rapid operationof the selector switches, or by other physical abuses of the machine causing shock and/or vibrations to the arious mechanisms. Many different approaches have been tried to overcome the above deficiency, but in the case of using basically mechanical parts to overcome these problems,'the different number of solutions has placed a burden .on machine users who either have to stock a large number of difi'erent replacement parts or suffer substantial losses of revenue from machines which are cies of the electromechanical parts described above.

- U.S. Pat. No. 3,451,518 uses all solid state circuitry,

however, this design has a number of limitations. After completion of a vend cycle, a capacitor must be recharged before another cycle can be started. This limits the operating speed of the machine. As the fully charged capacitor impresses a high voltage across the merchandise release actuators (SCRs), line transients and electrical noise need only be large enough to make up the difference between the capacitor charge voltage and the SCR breakover voltage in order to create false vending operations. Also, the charge on the capacitor can be a safety hazard for service personnel for a time after the machine has been disconnected from the power line. In additiomthe unit uses substantial power during standby.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is designed to overcome many of the difficulties encountered with mechanical dispensing mechanisms and with some attempts of the prior art to design solid state vending machine control circuits. Although the particular control circuit shown will be described in connection with a vending operation, obviously it has wider use.

Basically the invention includes a turn-on switch or terminal switch which is operated by the application of electrical power to the machine. When the terminal switch is in an on condition, the machine can receive coins and once a correct deposit of coins has been made in the machine the memory will be placed in an activated condition with the memory subsequently turning on the main power switch for use in the vending operation. When the main power switch has been turned on, the terminal switch is turned off so that no further coins may be deposited until the vending cycle has been completed. The main power switch provides the operating voltages for the commodity selection switches and the dispensing solenoids or other electrical dispensing apparatus. Once a particular commodity selection switch has been operated, the dispensing operation will follow. There is a delay interval built into the circuit such that the terminal switch will again be placed in an on" condition, the memory erased and the main power switch turned off a predetermined period fater the commodity selection has been made. In addition, to prevent burn-out of those components which are only rated for intermittent use, the terminal switch will be turned on and the main power switch turned off if no vending operation is completed in a predetermined interval, for example minutes after the machine is placed in a ready-to-vend condition.

FIG. 1 is a functional block diagram of one form of the invention. A crediting terminal power switch (TSM) is indicated at 10 and is connected by a line 12 to the crediting terminal portion of the coin mechanism indicated at 14. The crediting terminal 14 is connected by a line 16 to a memory 18 with the memory 18 being connected by a line 20 to a main power switch (PSM) indicated at 22 and by a line 19 to the TSM. The PSM is in turn connected by a line 24 to the TSM and by lines 26 and 28 to commodity selection switches 30 and the solenoid power switches 32. A line 34 connects the commodity selection switches 30 to the solenoid power switches 32. The dispensing solenoids are indicated at 36 and are connected by a line 38 to the solenoid power switches. The diagrammatic illustration of FIG. I is completed by a timing circuit 40 which is connected to the solenoid power switches by a line 42 and is connected to the TSM by a line 44.

When electric power is applied to the control circuit, the TSM 10 is placed in an on" condition. This enables the coin receiving mechanism to be placed in an activated condition or in a condition to receive coins in the normal manner. Once credit is established in the crediting terminal 14 by the deposit of a correct amount of coins, the memory 18 will be activated. Activation of the memory turns the PSM 22 to an on condition, which in turn turns the TSM to an "off" condition. With the TSM in an off condition, no further coins will be accepted until the vend cycle is completed. The application of power to the PSM applies an operating voltage to both the commodity selection switches and to the solenoid power switches. The operation of one of the commodity selection switches then causes one of the dispensing solenoids to operate to vend a particular chosen article. Simultaneously with the application of power to one of the dispensing solenoids, through the solenoid power switches, the timing circuit 40 is operated with the result that the TSM is again placed in an on condition after a predetermined delay. The delay involved, which may be on the order of 500 milliseconds, is sufficient for the vending operation to be completed by the electromechanical dispensing means. When the TSM is again placed in an on condition, the memory is erased which in turn causes the PSM to be placed in an off condition, thus readying the control circuit for the start of another vending cycle.

FIG. 2 details the control circuit diagrammatically illustrated in FIG. 1. The commodity selection switches 30 are individually indicated at 30a, 30b, 30c, 30d, 30c and 30f. The solenoid power switches 32 each include an SCR 46 with the gate 48 of the SCR being connected to the parallel combination of a resistor 50 and a capacitor 52. The anode 54 of each SCR is connected through a capacitor 56 to the cathode 58. All of the cathodes are connected in common to line 60.

The dispensing solenoids 36 each have coils indicated at 3611-36). Sold-out switches are indicated generally at 62 with the switches being individually designated as switches 62a through 62f. The sold-out switches 62 are each connected to one side of a coil of one of the dispensing solenoids which in turn are each connected to the anode of one of the SCRs 46 forming the solenoid power switches. The top terminals of each of the sold-out switches 62 are connected in common to line 64.

The control circuit is connected to a conventional AC source of electrical power by lines and 72. A filter network is connected between lines 70 and 72 and includes a resistor 74 connected to a capacitor 76, and a second capacitor 78 connected to a resistor 80. In parallel with the filter network is a pair of SCRs 82 and 84. The gates of SCRs 82 and 84 are connected respectively to resistors 86 and 88, a capacitor 90 and a diode 92. The right-hand side of resistors 86, 88, capacitor 90 and diode 92 are connected in common to a resistor 94 and a diode 96. Resistor 94 is connected to a diode 98 which in turn is connected to a pair of resistors 100 and 102, with the bottom side of resistor 102 being connected to a capacitor 104 and to a neon lamp 106. The bottom of capacitor 104 is connected through diode 108 to line 72. A resistor 110 and a capacitor 112 are connected between lines 70 and 72.

A portion of the coin mechanism for the vending machine is indicated generally at 114 and includes a coil 116 connected to line 70 and to the anode of a diode 1 18. The cathode of diode 118 is also connected to line 70. The anode of diode 118 is connected to the anode ofa diode 120 which in turn has its cathode connected to the anodes of diodes 122 and 124. A credit switch is indicated at 126 and is connected to the bottom side of capacitor 112 and to the anode of diode 96. Normally, the credit switch will close when an appropriate amount of coins have been deposited in the coin receptacle. The coil 116 is a part of the coin return electromagnet.

The gate of SCR 124 is connected to the neon lamp 106 and to the parallel combination of a capacitor 128 and a resistor 130. The bottom side of capacitor 128 and resistor 130 are connected to line 72 and to the anode of a diode 132. The parallel combination of a capacitor 134 and a resistor 136 are connected to one side of a neon lamp 138 which in turn is connected to the cathode of diode 122. The bottom side of capacitor 134 is connected to the top of resistor 130 and the bottom side of resistor 136 is connected to the parallel combination of capacitor 140 and resistor 142 and to the cathode of the diode 144. The anode of diode 144 is connected to the cathode of diode 132 and to resistor 146. The bottom of resistor 146 is connected to a second resistor 148 with the junction between resistors 146 and 148 being connected to the commodity selection switches 30.

A diode 150 has its cathode connected to the top of capacitor 128 and resistor 130 and has its anode connected to a capacitor 152 and to a resistor 154. Resistor 154 in turn is connected to a neon lamp 156 with the opposite side of neon lamp 156 being connected through a resistor 158 to the cathode of diode 150. The circuit is completed by a resistor 160 connected to line and to the anode of a diode 162. The cathode of diode 162 is connected to line 70.

In operation, assuming the vending machine has been filled with-products, power is initially applied to lines and 72. When line 70 is sufficiently positive with respect to line 72, current will flow through diode 108, the cathode gate junction of SCR 124, capacitor 134, neon lamp 138, diodes 122 and and the coil 116 of the coin return electromagnet which is a part of the coin mechanism 114. The values of the components, capacitor 134, capacitor 128, resistor and the neon lamp 138 may be chosen so that conduction of SCR 124 will occur only at a predetermined level of applied voltage. In this way, the coin return electromagnet, which has to be energized before the vending machine will accept coins, will never accept coins when the applied power is too low for the dispensing solenoids to function properly.

Once SCR 124 is triggered into condition, it will stay in conductionfor the remaining portion of the half cycle in which line 70 is positive relative to line 72. SCR 124 will turn off when the current through coil 116 nears zero. During the time that line 70 is negative with respect to line 72, the energy stored in coil 116 will cause current to flow through diode 118 to keep the coin return electromagnet energized until SCR 124 again conducts during the next half cycle of the applied voltage.

Current flowing through SCR 124 also flows through diode 98, resistor 94, capacitor 90 and diode 92, which are arranged in parallel, and through capacitor 76 and resistor 74. The gates of SCRs 82 and 84 will remain at a negative potential with respect to their cathodes to increase the SCRs blocking capability and also to prevent a positive charge from building up on capacitor 90 and triggering an SCR into unwanted conduction. As

indicated above, the combination of resistors 80 and 74 and capacitors 78 and 76 function as a filter to remove line voltage transients.

SCR 124, which functions as the TSM, will remain in a conducting condition until enough coins are inserted into the coin mechanism to cause the credit switch 126 to close. The switch closure itself only lasts for a few periods of line voltage. During the time that the switch is closed and when line 70 is negative with respect to line 72, current will flow through diode 162, resistor 148, resistor 146, the cathode gate junction of SCR 84, the parallel combination of resistor 88 and capacitor 90, diode 96, credit switch 126 and resistor 110. This current flow will trigger SCR 84 into conduction. With this SCR conducting there will then be current flow through the cathode gate junction of SCR 124, the parallel combination of capacitor 128 and resistor 130, capacitor 134, resistor 136 and diode 144. This current will not, however, trigger SCR 124 into conduction because at this time its anode is not positive. Capacitor will charge very nearly to line voltage and this charge will, acting through resistor 136, bias neon lamp 138 so that it will not fire during the next positive half cycle. With SCR 124 held in a non-conducting condition, coil 1 16 will not receive current and thus the coin return electromagnet in the coin mechanism itself will reject any further coins should they be deposited.

The gate drive for SCR 84 is provided by capacitor 90 which functions as the memory in the circuit. SCRs 84 and 82 will alternately conduct on alternate half cy cles of the applied AC voltage with capacitor 90 providing the gate drive for both SCRs. Capacitor 90 stores energy when the gate of the conducting SCR becomes the source and uses this energy to trigger the other SCR into conduction as soon as the line voltage reverses polarity. Thus, SCRs 82 and 84 function as the main power switch or PSM. With SCRs 82 and 84 conducting, SCR 124 or the TSM will be held in a nonconducting condition. The memory places the PSM in an on condition which places the TSM in an off" condition.

When SCRs 82 and 84 conduct, the current flowing through resistors 148 and 146 establishes a potential at their junction. This potential is applied directly to the commodity selection switches 30. When any one of the commodity selection switches 30 is momentarily depressed, it will apply positive potential to the gate 48 of any one of the SCRs 46 and thus trigger this particular SCR into conduction. Current will then flow through a dispensing solenoid 36, and assuming the sold-out switches are closed, to common line 64. The dispensing mechanism will be activated by one of the solenoids 36 and the particular SCR 46, once triggered, will continue to conduct due to the action of diode 132 which permits reactive current flow through the SCR during the time that the applied current falls to zero. The same current also flows through resistor 160, with the result that the potential developed across this resistor elevates all of the solenoid power switches 32 sufficiently above ground to prevent the application of a positive potential to a second SCR by means of a commodity selection switch. Thus, the circuit effectively eliminates activation of more than one dispensing mechanism for each closure of the credit switch.

The potential generated across resistor charges capacitor 152 through resistor 154 until SCR 124 is triggered. The time for capacitor 152 to charge until the point where SCR 124 is triggered, is the time available for the dispensing mechanism to operate. It may be adjusted as needed by selection of values for resistor 154 and capacitor 152, with this combination of elements forming the timing circuit 40.

The triggering of SCR 124 permits memory capacitor 90 to discharge through diode 98 and resistor 94.

Whichever one of SCRs 82 or 84 which is conducting at this time will turn off at the end of the particular halfcycle and the other SCR will not be retriggered on the next half-cycle due to the absence of positive gate drive because of the discharge of capacitor 90. With both SCRs 82 and 84 in a non-conducting state, no current can flow through the dispensing solenoid nor the solenoid power switches and thus no further commodities can be vended. The operation of the TSM (SCR 124) has erased the memory (capacitor 90) and turned off the PSM (SCRs 82 and 84).

At the same time capacitor 140 will discharge through resistor 142 and allow neon lamp 138 to ionize. The resulting current pulse will again trigger SCR 124. When SCR 124 is in an on condition, power will be resupplied to the coin return electromagnet coil 1 l6 and thus the machine is again ready to operate and accept coins.

As indicated previously, one of the problems with previously-known vending machines was that it was possible in some cases to manipulate the power applied to the machine during a vend cycle to cause the dispensing solenoid to release and reenergize before the controlling relays can act to prevent this and double the normal product may be dispensed. The circuit of FIG. 2 prevents such a possibility in the SCRs 82 and 84 cannot be retriggered immediately after a short term power interruption. The filter network consisting of resistors 74 and 80 and capacitors 76 and 78 assist SCRs 82 and 84 in turn-off and prevent fast rising reapplied voltage from turning them back on. The solenoid power switches will maintain the dispensing solenoids in an energized condition until all stored energy has been released. Before the solenoid releases and the solenoid power switch turns off, memory capacitor 90 has had ample time to discharge, thus returning the control circuit to a normal condition in which SCR 124 is conducting and is ready to receive a new coin deposit.

In order to prevent damage to components of the vending machine itself, such as counters which are often rated for intermittent use, and to prevent unnecessary service calls, both of which may result if there were a long delay while the machine remained in a ready-to-vend condition, after credit has been established, as indicated above, SCR 124 (TSM) is placed in a non-conducting state. Capacitor 104 now begins to charge through resistors 102 and 100, diode 120 and coil 116. When the ionizing potential of neon lamp 106 has been reached, it will ionize and trigger SCR 124 into conduction with the result that the machine will be reset to a stand-by condition in which it can again accept coins. Normally the time for capacitor 104 to charge may be set on the order of approximately minutes.

An additional feature of the circuit described above concerns protection against damage in the case of a shorted dispensing solenoid. If one of the solenoids 36 should become shorted, the potential across resistor 160 would exceed the ionizing voltage of neon lamp 156, thus SCR 124 would be triggered into conduction and would limit the duration of the short circuit current through the dispensing solenoid to one half cycle of the applied sine wave. By so limiting the current, there is little likelihood of damage to any of the components.

FIGS. 3 and 4 disclose a second embodiment of the invention. A crediting terminal power switch is indicated at 170 and again may be designated as the TSM.

The TSM is connected by a line 172 to the crediting terminal portion of the coin mechanism indicated at 174. The terminal 174 is connected by a line 176 to the memory 178. The memory is connected by line 180 to the TSM and performs a function similar to that described above, in that after the memory has been activated by an appropriate deposit of coins in the coin mechanism, it is effective to turn the TSM to an off condition. The memory is connected by a line 182 to a main power switch or PSM indicated at 184.

The main power switch 184 is connected by a line 186 to a series of commodity selection switches 188 which are in turn connected by a line 190 to a secondary power switch 192 which performs a function similar to the solenoid power switches of FIGS. 1 and 2. The main power switch is also connected by a line 191 to the secondary power switches 192. The secondary power switch 192 is connected by a line 194 to a dispensing mechanism 196 and by a line 198 to a clamp 200. The clamp 200 is connected in turn, by a line 202, to the memory 178, by a line 204 to the TSM, and by a line 201 to the commodity selection switches 188.

In operation, the initial application of electrical power turns the TSM to an on condition. An appropriate deposit of coins in the crediting terminal portion of the coin mechanism 174 activates the memory 178. When the memory is activated, the main power switch is placed in an on condition and the TSM is placed in an off condition. Operation of the main power switch places an appropriate voltage at the input of the commodity selection switches 188 so that upon operation of any one of said switches, a secondary power switch 192 is operated. Operation of a secondary power switch 192 causes a dispensing mechanism to operate and at the same time clamps the voltage applied to the commodity selection switches such that no further operation of a commodity selection switch will cause operation of a dispensing mechaism. The clamp also initiates a memory timing cycle, effectively the discharge of a capacitor, at the end of which the crediting terminal power switch is placed in an on condition and the main power switch is placed in an off condition. This completes the vend cycle and the machine is now ready again to accept coins and to repeat the vending operation.

Turning specifically to FIG. 4, the input lines are indicated at 206 and 208. The commodity selection switches 188 are designated respectively 188a through 188f. In like manner, the secondary power switches 192 each have identical components associated with each of the commodity selection switches. Cam switches indicated generally at 210 include individual switches 210a through 210f. The dispensing mechanisms 196 also include individual coils 196a through 196f. In like manner there are a series of sold-out switches designated 212a through 2l2f.

Line 208 is connected to the top side of each of the sold-out switches 2120 through 2l2fand to resistor 214 fonning a portion of one of the secondary power switches. The remaining components in each of the secondary power switches include a capacitor 216 connected to resistor 214 and to one contact of a commodity selection switch 188. A capacitor 218 is connected to capacitor 216 and to a diode 220. A triac 222 has one terminal connected in common with the other triacs in the secondary power switches and connected to line 224. The other terminal of each of the triacs 222 is connected to the bottom of a cam switch 210.

A triac 228 has one of its terminals connected to line 224 and the other terminal connected to line 206. The gate of triac 228 is connected to a resistor 230, then through a capacitor 232 to line 206. A capacitor 234 is connected between the terminals of triac 228.

The coin mechanism is indicated generally at 236 and may include a coil 238 which is normally a part of the coin return electromagnet. A credit switch is indicated at 240 and is shown in the unoperated position.

A unijunction transistor 242 has its anode connected to the junction between resistor 244 and resistor 246. A resistor 248 is connected to the same junction and to the emitter of a transistor 250. The collector of transistor 250 is connected to the gate of an SCR 252. The gate of SCR 252 is also connected to a resistor 254 and then to line 208. A capacitor 256 is connected between the bottom side of resistor 254 and the anode of SCR 252. The anode of SCR 252 is connected through a resistor 258 to the junction of resistor 230 and capacitor 232.

The gate of unijunction transistor 242 is connected through resistor 260 and a diode 262 to the junction of resistor 264 and capacitor 266, with the bottom side of the capacitor being connected to line 208. The top side of resistor 264 is connected through a diode 268 to the normally open terminal of the credit switch 240.

An SCR 270 has its anode connected to line 206 and its cathode connected to a diode 272, with the anode of diode 272 being connected to line 208. The gate of SCR 270 is connected through a resistor 274 to the cathode of SCR 270. The gate of SCR 270 is also connected through a diode 276 and a resistor 278 to a terminal of unijunction transistor 242.

The bottom side of resistor 278 is connected through a pair of oppositely-connected diodes 280 and 282 to a resistor 284 which is in parallel with a normally-open switch 286. The bottom of resistor 284 is connected through resistors 288 and 290 to line 208.

The junction between oppositely-connected diodes 280 and 282 is connected to the cathode of diode 292 with the anode of diode 292 being connected to the top of series-connected diodes 294, 296 and 298. The anode of diode 292 is also connected to the anode of diode 300 which has its cathode connected through a resistor 302 to line 208. The anode of diode 300 is also connected through a resistor 304 and a diode 306 to a resistor 308 connected at its top side to one terminal of triac 228.

An SCR 310 has its cathode connected to line 208 and its gate connected through resistor 312 to line 208. The gate of SCR 310 is also connected through a neon lamp 314 and a resistor 316 to line 318, which is connected, at its other end, to the common cathodes of diodes 220. A resistor 320 is connected to the anode of diode 322 which has its cathode connected to the anode of SCR 310. A capacitor 324 is connected to the top side of neon lamp 314 and at its bottom side to line 208 and a capacitor 326 is connected at its bottom side to line 208 and at its top side to line 318.

When AC power, preferably 110 volt AC, is first applied to terminals 206 and 208, current will flow through resistor 249 connected at its upper side to line 206, the normally closed contacts of switch 240, diode 245, resistor 244 and resistor 246. The anode of unijunction transistor 242 is connected to the junction of resistors 244 and 246 and as soon as that junction becomes positive with respect to the gate of transistor 242, transistor 242 will turn on and current will pass through resistor 251 connected at the bottom of transistor 242. As the voltage drop across resistor 215 increases, current will begin to flow from line 208 through coil 238 of the coin return electromagnet and through the cathode gate junction of SCR 270, in parallel with resistor 274, and then through diode 276, resistor 278 and through transistor 242 to line 206. As soon as this current flow satisfies the turn-on requirements of SCR 270, it will turn on and conduct current through coil 238 of the coin return electromagnet. The turning on of SCR 270 is in effect the turning on of the TSM or the crediting terminal power switch, described above in connection with FIG. 3. As soon as current flows through coil 238, placing the coin return electromagnet in a condition to accept coins, the machine is ready to operate.

After the correct amount of coins has been inserted into the coin receptacle, the vend switch 240 will move from its normally closed position shown in FIG. 4, to close upon the normally open contact. This change in the position of switch 240 will cause memory capacitor 266 to be charged to the peak of line voltage through diode 268 and resistor 264. At the same time current through transistor 242 flowing through the normally closed contacts of switch 240 will be interrupted. When transistor 242 ceases to conduct, it removes the gate drive from SCR 270 which in effect turns off the TSM. This will result in the removal of current through the coin return electromagnet coil 238 which prevents the coin mechanism from receiving any further coins or will cause the coin mechanism to reject any coins which are thereafter inserted.

In normal operation, switch 240 will quickly return to its normally-closed position which will re-establish the positive voltage at the anode of transistor 242. However, transistor 242 cannot now conduct since its gate is removed from ground by the back-biased diode 262. Accordingly, the voltage at the junction of resistor 244 and resistor 246 will rise to a more positive potential than was previously possible. Such a positive rising potential is impressed across transistor 250 after this potential exceeds approximately 10 volts, depending upon the values selected for various circuit components. The emitter-collector junction of transistor 250 will now break down and allow trigger current to flow through the cathode gate junction of SCR 252.

Current flowing through the cathode gate junction of SCR 252 will cause it to be triggered into conduction whenever line 208 is negative with respect to line 206. Current through SCR 252 will supply charging current to capacitor 232, establishing a negative potential at the gate of triac 228. Such a negative potential at the gate of the triac will supply the necessary bias to trigger triac 228 into an on" condition. Triac 228 functions as the main power switch or PSM and once it is in the on condition, the circuit is in a ready-to-vend condition. Note that at this time the TSM has been placed in an off condition and that the operation of placing SCR 270 in an off condition and the ultimate placing of triac 228 in an on condition is initially brought about because memory capacitor 266 begins to charge as soon as switch240 closes upon its normally open contact.

With triac 228 being in an on or conducting condition, a voltage positive with respect to line 208 is applied through diodes 298, 296 and 294 to the commodity selection switches 188. This string of diodes is effective to insure that even a momentary activation of one of the commodity selection switches will be sufficient to trigger one of the secondary power switches into full conduction.

After the system has been brought to the condition described above, in which it is ready to vend, the closing of any one of the commodity selection switches will establish current flow from line 208, through one of the normally-closed sold-out switches, through one of the coils 196, which may be a part of a solenoid or motoroperated dispensing mechanism, through the cam switch associated with a motor operated dispensing mechanism and to the gate junction of one of the traics 222. Current flowing through the gate junction of triac 222 will cause the triac to conduct which in turn will then energize the coil of the dispensing mechanism. As soon as the line voltage reverses and triac 222 changes to an of condition, it will be retriggered by current caused to flow through the gate junction of triac 222 and capacitor 218 and resistor 214 by the energy stored in the winding of the motor or solenoid powering the dispensing mechanism. In this way, the secondary power switch is latched into conduction and is effectively independent of the commodity selection switch, once it has been closed.

The turning on of triac 222 will cause the anode of diode 220 to move in a positive direction, impressing a voltage across neon lamp 314. When this lamp ionizes, current will flow through the cathode gate junction of SCR 310, through resistor 316, diode 220, the triac 222 and triac 228. This current flow will trigger SCR 310 into conduction. Once this condition has been reached, the positive trigger voltage for the commodity selection switches is clamped through diode 292 at a low value so that no further secondary power switches can be triggered. Effectively SCR 310 functions as a clamp to maintain the voltage applied to the commodity selection switches at such a value that no further vending operation can take place, even if further commodity selection switches are closed.

As soon as SCR 310 is placed in a conducting condition, the memory or timing capacitor 266 begins to discharge through diode 282, resistor 284 and resistor 288. The gate of SCR 270 will be clamped, preventing it from being triggered and capacitor 326 will be discharged through resistor 320 and diode 322. As indicated previously, when the clamp is operated, it is effective to initiate operation of the memory cycle, the discharge of capacitor 266. Since the hold capacitor, or capacitor 326, will be recharged every half cycle, as long as triac 228 is in an on" condition, SCR 310 will remain conducting.

When capacitor 266 is sufiiciently discharged to allow the anode of unijunction transistor 242 to go positive with respect to its gate, it will turn on and prevent the voltage at the junction of resistor 244 and 246 from rising enough to cause an emitter-collector breakdown oftransistor 250. As explained above, this will withhold triggering current from SCR 252 which will in turn cause triac 228 to be placed in an off" condition. Thus, the discharge of the memory capacitor has placed the main power switch (PSM) in an off" condition.

With triac 228 in an of condition, triac 222 must also turn off as soon as the energy in the magnetic portion of the circuit has been dissipated. If the mechanism powered by coil 196 is a motor, then the rotating cam will have closed the cam switch which will keep the motor running until a full cycle has been completed. The cam switch and the junction of capacitor 326 and resistor 320 are connected so that a jammed motor will either prevent the machine from accepting any additional coins, thus calling attention to a malfunction, or will not affect the operation of the remaining parts of the machine, if service cannot be made immediately available.

As described above, the memory capacitor 266 turns off the PSM and at the same time, after it has fully discharged, permits transistor 242 to again turn on, which has the ultimate result, as described above, of placing SCR 270 in an on" condition, which then places the entire vending machine in a condition to accept a new coin deposit.

In the event of an attempt to vend from a stack which is empty, the sold-out switch will be in an open position and thus no vending operation can take place. When a commodity selection switch is depressed, gate current cannot flow through SCR 222 and the machine will remain in a ready-to-vend condition. In this connection, occasionally a machine is inadvertently left in a readyto-vend condition. if no vend is made from the machine, then resistor 290 will discharge capacitor 266 over a period of 15-20 minutes to cause the machine to again return to a condition to accept a coin deposit.

Many times there will be a significant drop in voltage during the time the machine is ready to vend. This may be caused by the machines compressor starting, or by similar demands on the line, or it may be caused by a momentary loss of power. A loss of credit information is prevented by the unique connection of capacitor 266 in the drive circuit for transistor 242. The capacitors charge is made independent of the continuous application of line voltage so that a power interruption will have no influence if power is restored within approximately 10 minutes.

An important feature of the dispensing portion of the circuit is its inherent self-protection. Should a near short circuit occur in the dispensing mechanism, triac 222 can be triggered in the normal manner, but the resulting current surge will be limited to the k cycle or less, since there then will be no energy stored when the winding is shorted out and thus triac 222 cannot be latched into conduction. Neither can it be retriggered by the commodity selection switch, since the trigger signal is available only for r5 cycle or less. The normal wiring impedance of the vending machine itself and its supply lines will limit the surge current to a reasonable value, not destructive to the wiring or the various solid stage devices, as long as the current surge is limited to a maximum of A cycle.

Various others of the numerous components initially described in the circuit perform important functions. For example, capacitor 247 is effective to bypass any noise generated in the coin mechanism. Diode 272 prevents chattering of the coin return electromagnets. Capacitor 256 prevents noise pulses from accidentally triggering SCR 252 which would have the effect of ini tiating the machine toward a ready-io-vend condition. Capacitor 234 performs the same function for triac 228. Capacitor 324 slows the reaction of neon lamp 364 to assure that one of the triacs 222 has been turned to an on" condition before reset is initiated. The normally open switch 286 is effective to allow a choice of vend time if it is placed in the closed condition.

The block diagram of FIG. is substantially the same as the block diagram of FIG. 1 and like parts have been given the same number. The only difference between the two diagrams is that there is a direct connection between the timing circuit 40 and the memory 18, which connection is designated by line 45. Line 44 connecting the timing circuit and the crediting terminal power switch has been eliminated and there is no longer a connection, exemplified by line 19, between the crediting terminal power switch and the memory 18. In all other respects the two block diagrams are identical.

FIG. 6 is an electrical schematic corresponding to the block diagram of FIG. 5. It is substantially the same as the schematic of FIG. 2, expect that the commodity selection switches, solenoid power switches, dispensing solenoids and sold-out switches have not been repeated. Like parts have again been given like numbers. Diodes 98 and 122 from FIG. 2 have been eliminated, as has neon bulb 138 and resistors 100, 136 and 142. Also, capacitors 134 and 140 have been eliminated. There have been two additions. A resistor 340 is connected on one side to the bottom of capacitor 112 and on the other side to credit switch 126. A second resistor, designated at 342, is connected between the top of resistor 110 and the cathode of diode 144. In all other respects, the circuits of FIGS. 2 and 6 are identical.

SCR 124 in the circuit of FIG. 2 performs the function of the crediting terminal power switch in that when this SCR is placed in a conducting condition, power is supplied to the coin return electromagnets so that a coin deposit may be made. SCR 124 does not perform this function in the circuit of FIG. 6. Instead, when power is applied to the circuit at lines 70 and 72, current will flow through resistor 110, resistor 342, diode 120 and coil 116. As before, diode 118 will prevent chattering during the other half cycle of the applied AC signal. The coin return electromagnet, coil 116, will be energized and thus a coin deposit may be made.

After an appropriate coin deposit has been made and credit has been established, the credit switch will charge the memory capacitor, as before, and the charge of this capacitor, as described previously, will effectively place the main power switch in an on" condition. However, current flowing through resistor 342 will now flow through diode 144, instead of diode 120, with the result that the coin return electromagnet will be de-energized and therefore no further coin deposits can be made until a vending operation has taken place. Thus, diodes 120 and 144 perform the function of the crediting terminal power switch.

The circuit will now operate as described in connection with the operation of the circuit of FIG. 2 up to and including the discharge of capacitor 90. However, at the end of the vend cycle, after capacitor 90 has been discharged, through SCR 124, the main power switch will be turned off and SCR 124 will be turned off. Current will then flow through resistor 342 and diode 120 and through the'coin return electromagnet coil 116. Thus, the coin return electromagnet is again energized and the circuit is ready to accept a new coin deposit. SCR 124 functions as a part of the reset means or timing circuit for the memory and not as the crediting terminal power switch.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there may be many modifications, substitutions and alterations thereto.

I claim:

1. A control circuit for use in a vending machine having coin receiving means, commodity selection switches, and an electrically operated dispensing means, said control circuit including solid state terminal switch means (TSM) arranged to be placed in an on condition in response to the application of electric power to said control circuit, the coin receiving means being placed in a condition to receive coins when said TSM is in an on condition,

memory means connected to the coin receiving means,

solid stage power switch means (PSM) connected in circuit with said memory means and being placed in an on condition by the activation of said memory, said TSM being placed in an off condition when said PSM is placed in an on condition, the placing of said PSM in an on condition providing a voltage adapted for use in connection with the commodity selection switches and the electrically operated dispensing means,

and timing means connected in circuit with said TSM and PSM for placing said PSM in an off" condition if a commodity selection switch has not been operated a predetermined interval after the PSM is placed in an on condition.

2. The control circuit of claim 1 further characterized by a connection between said PSM and said TSM for placing said TSM in an of condition when said PSM is in an on condition.

3. The circuit of claim 2 further characterized in that said PSM includes an SCR.

4. The circuit of claim 2 further characterized in that said PSM includes a pair of SCRs operating on alternate half cycles of the applied electric power.

5. The circuit of claim 2 further characterized by and including a filter circuit connected between the source of electric power and said PSM, said filter circuit preventing operation of said PSM immediately upon the application of electric power to said control circuit.

6. The circuit of claim 2 further characterized by and including timing circuit means placing said TSM in an on condition and said PSM in an off condition a predetermined interval after operation of a dispensing means.

7. The circuit of claim 2 further characterized in that said memory includes a capacitor providing the driving voltage for said PSM.

8. The circuit of claim 7 further characterized in that said PSM includes a pair of SCRs conducting on alternate half cycles of the applied electric power.

9. The control circuit of claim 2 further characterized by and including solid state power swtiches connected to said PSM and to the commodity selection switches, the operation of a commodity selection switch, turning a solid state power switch to an on condition to supply power to the electrically operated dispensing means.

10. The control circuit of claim 9 further characterized in that the operation of a commodity selection switch reduces the voltage applied from the PSM to the commodity selection switches to prevent further dispensing operations upon the operation of an additional commodity selection switch.

11. The control circuit of claim 10 further characterized in that said solid state power switches each include an SCR connected to one of the commodity selection switches.

12. The control circuit of claim 1 further characterized by a connection between said memory and TSM and PSM, activation of said memory in response to a coin deposit placing said TSM in an off" condition and said PSM in an on" condition.

13. The circuit of claim 12 further characterized in that said TSM includes an SCR.

14. The circuit of claim 12 further characterized by a plurality of solid state power switches connected between the commodity selection switches and said PSM, said PSM including a triac connected in common to each of said solid state power switches.

15. The control circuit of claim 14 further characterized in that each of said solid state power switches include a triac.

16. The circuit of claim 12 further characterized by a clamp circuit connected to the commodity selection switches, TSM and memory, operation of a commodity selection switch effectively causing said clamp circuit to change the voltage applied to the commodity selection switches to prevent an additional dispensing operation upon the operation of a second commodity selection switch.

17. The circuit of claim 16 further characterized by and including solid state power switches connected to the commodity selection switches and to said clamp circuit, the operation of a commodity selection switch placing one of said solid state power switches in an on condition, which in turn places said clamp circuit in an on condition.

18. The control circuit of claim 17 further characterized in that said clamp is connected to said memory and said TSM, placing of said clamp circuit in an on condition initiates operation of the memory circuit to place said PSM in an off" condition and said TSM in an on condition.

19. The control circuit of claim 17 further characterized in that said clamp includes circuit means preventing operation of the TSM for a predetermined time interval after said clamp circuit is placed in an on condition. 

1. A control circuit for use in a vending machine having coin receiving means, commodity selection switches, and an electrically operated dispensing means, said control circuit including solid state terminal switch means (TSM) arranged to be placed in an ''''on'''' condition in response to the application of electric power to said control circuit, the coin receiving means being placed in a condition to receive coins when said TSM is in an ''''on'''' condition, memory means connected to the coin receiving means, solid stage power switch means (PSM) connected in circuit with said memory means and being placed in an ''''on'''' condition by the activation of said memory, said TSM being placed in an ''''off'''' condition when said PSM is placed in an ''''on'''' condition, the placing of said PSM in an ''''on'''' condition providing a voltage adapted for use in connection with the commodity selection switches and the electrically operated dispensing means, and timing means connected in circuit with said TSM and PSM for placing said PSM in an ''''off'''' condition if a commodity selection switch has not been operated a predetermined interval after the PSM is placed in an ''''on'''' condition.
 2. The control circuit of claim 1 further characterized by a connection between said PSM and said TSM for placing said TSM in an ''''off'''' condition when said PSM is in an ''''on'''' condition.
 3. The circuit of claim 2 further characterized in that said PSM includes an SCR.
 4. The circuit of claim 2 further characterized in that said PSM includEs a pair of SCRs operating on alternate half cycles of the applied electric power.
 5. The circuit of claim 2 further characterized by and including a filter circuit connected between the source of electric power and said PSM, said filter circuit preventing operation of said PSM immediately upon the application of electric power to said control circuit.
 6. The circuit of claim 2 further characterized by and including timing circuit means placing said TSM in an ''''on'''' condition and said PSM in an ''''off'''' condition a predetermined interval after operation of a dispensing means.
 7. The circuit of claim 2 further characterized in that said memory includes a capacitor providing the driving voltage for said PSM.
 8. The circuit of claim 7 further characterized in that said PSM includes a pair of SCRs conducting on alternate half cycles of the applied electric power.
 9. The control circuit of claim 2 further characterized by and including solid state power swtiches connected to said PSM and to the commodity selection switches, the operation of a commodity selection switch, turning a solid state power switch to an ''''on'''' condition to supply power to the electrically operated dispensing means.
 10. The control circuit of claim 9 further characterized in that the operation of a commodity selection switch reduces the voltage applied from the PSM to the commodity selection switches to prevent further dispensing operations upon the operation of an additional commodity selection switch.
 11. The control circuit of claim 10 further characterized in that said solid state power switches each include an SCR connected to one of the commodity selection switches.
 12. The control circuit of claim 1 further characterized by a connection between said memory and TSM and PSM, activation of said memory in response to a coin deposit placing said TSM in an ''''off'''' condition and said PSM in an ''''on'''' condition.
 13. The circuit of claim 12 further characterized in that said TSM includes an SCR.
 14. The circuit of claim 12 further characterized by a plurality of solid state power switches connected between the commodity selection switches and said PSM, said PSM including a triac connected in common to each of said solid state power switches.
 15. The control circuit of claim 14 further characterized in that each of said solid state power switches include a triac.
 16. The circuit of claim 12 further characterized by a clamp circuit connected to the commodity selection switches, TSM and memory, operation of a commodity selection switch effectively causing said clamp circuit to change the voltage applied to the commodity selection switches to prevent an additional dispensing operation upon the operation of a second commodity selection switch.
 17. The circuit of claim 16 further characterized by and including solid state power switches connected to the commodity selection switches and to said clamp circuit, the operation of a commodity selection switch placing one of said solid state power switches in an ''''on'''' condition, which in turn places said clamp circuit in an ''''on'''' condition.
 18. The control circuit of claim 17 further characterized in that said clamp is connected to said memory and said TSM, placing of said clamp circuit in an ''''on'''' condition initiates operation of the memory circuit to place said PSM in an ''''off'''' condition and said TSM in an ''''on'''' condition.
 19. The control circuit of claim 17 further characterized in that said clamp includes circuit means preventing operation of the TSM for a predetermined time interval after said clamp circuit is placed in an ''''on'''' condition. 